Introduction
The Boeing Phantom Eye is a high altitude, long endurance (HALE) unmanned aerial vehicle hydrogen-powered spy plane developed by Boeing Phantom Works.
The aircraft is Boeing’s proposal to meet the demand from the US military for unmanned drones designed to provide advanced intelligence and reconnaissance work, driven by the combat conditions in Afghanistan in particular.

Development
The Phantom Eye is an evolution from Boeing’s earlier success with the piston-powered Boeing Condor that set several records for altitude and endurance in the late 1980s. Boeing has also been studying a larger HALE UAV that can fly for over 10 days and carry payloads of 2,000 pounds (900 kg) or more; the company is also working on the Phantom Ray UAV as a flying testbed for advanced technologies.

Phantom Eye’s propulsion system successfully completed an 80-hour test in an altitude chamber on March 1, 2010; this cleared the way for the propulsion system and the airframe to be assembled. Boeing has worked closely with Ball Aerospace, Aurora Flight Sciences, Ford Motor Co. and MAHLE Powertrain to develop the Phantom Eye.

The Phantom Eye was revealed to the press at a ceremony at Boeing’s facilities in St Louis, Missouri, on July 12, 2010. The Phantom Eye demonstrator is a 60%-70% scale design of an objective system. According to Darryl Davis, president of Boeing’s Phantom Works advanced concepts group, the Phantom Eye demonstrator could lead to an objective system capable of achieving 24-hours-a-day, seven-days-a-week coverage of an area year round with up to four aircraft.

The demonstrator was shipped to NASA’s Dryden Flight Research Center at Edwards Air Force Base, California, for ground tests. It conducted its first medium-speed taxi test there on March 10, 2012, reaching speeds of 30 knots. Boeing declared the test a success and said it paved the way for the aircraft’s first flight, expected to last 8 hours.

The Phantom Eye completed its first flight on June 1, 2012 at Edwards Air Force Base. It reached a altitude of 4,000 ft and a speed of 62 knots (115 km/h) for 28 minutes. Phantom Eye’s landing gear dug into the dry lakebed and caused some damage to the aircraft.

On February 6, 2013, the Phantom Eye completed taxi testing at Edwards Air Force Base in preparation for the second flight. Sitting atop a launch cart, it reached speeds of 46 mph. In response to the first flight test, autonomous flight systems were upgraded and the landing system was improved.

The Phantom Eye completed its second flight on February 25, 2013 at Edwards Air Force Base. It climbed to an altitude of 8,000 ft at a cruising speed of 62 kn (71 mph) for 66 minutes. The second flight test ended with a successful landing.

Design
The Phantom Eye demonstrator has a 150-foot (46 meter) wingspan. Boeing states that it can fly for more than four days at a time at altitudes of up to 65,000 feet. Boeing also states that the Phantom Eye demonstrator will be able to carry a 450 pound payload and have a cruising speed of 150 knots. The Phantom Eye carries no armament and is for “persistent intelligence and surveillance”.

Propulsion
Each of the two propulsion systems consist of modified Ford 2.3 liter engines, reduction gearbox, and 4-blade propeller. The engines were originally designed for use with some models of the petrol-burning Ford Fusion car. To be able to run in the oxygen starved atmosphere at 65,000 ft, the engines feature a multiple turbocharger system that compresses that available low density air and reduces the radiated infrared heat signature to increase its stealth properties.

The engines, which provide 150 horsepower at sea level, have been tuned so as to be able to run on hydrogen. Boeing’s marketing department states that this will make the aircraft economical and “green” to run, as the only by-product will be water.